In the field of electronics, the interconnections between layers of a multilayer circuit are critical to the creation of high-density interconnection structures. These interconnection structures are used both for integrated circuit (IC) packaging and for the interconnection substrates to which IC packages are mounted. The interconnections within these structures are most commonly created by means of plated through-hole vias. High-density substrates are increasingly required for present and future generations of electronic products. Consequently, numerous methods have been described, developed and employed to facilitate the creation of the plated vias necessary for high-density substrates.
Typically, the metal plated vias are made as small as possible to conserve space for circuit routing. Often, the vias are made in “blind” fashion, where the via only extends partially through some but not all of the layers in the overall structure. Such methods can make uniform plating of all vias difficult. This is due to concerns over solution flow into the cavities and the potential for air entrapment, which can result in open circuit or unreliable interconnections.
Other previous attempts for making high-density vias and other interconnections have included: (1) use of conductive posts or metal or metal polymer composites which are designed to pierce the insulation material between layers during lamination to make interconnection from one layer to another, and (2) holes in insulation material filled with metal pastes that are designed to make connection between adjacent layer conductor elements.
In the drawings, the same reference numbers identify identical or substantially similar elements or acts. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 130 is first introduced and discussed with respect to FIG. 1). Any modifications necessary to the Figures can be readily made by one skilled in the relevant art based on the detailed description provided herein.